Surgical stapling apparatus with firing lockout mechanism

ABSTRACT

A surgical stapling device is provided which includes a first jaw supporting an anvil assembly and a second jaw supporting a cartridge assembly. The cartridge assembly supports a firing lockout assembly which includes a latch member having a blocking portion. The latch member is movable between a first position and a second position. In the first position, the blocking portion of the latch member is aligned with the stop surface of the drive member to prevent advancement of the drive assembly beyond an initial advanced position within the tool assembly and in the second position, the blocking member is misaligned with the stop surface of the drive member to permit subsequent advancement of the drive assembly within the tool assembly. In the retracted position of the drive assembly subsequent to firing of the surgical stapling device, the latch member is in the first position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/814,050, filed Mar. 10, 2020, the entire content of which is herebyincorporated by reference herein.

FIELD

This disclosure relates to surgical stapling apparatus. Moreparticularly, this disclosure relates to surgical stapling apparatushaving a firing lockout mechanism.

BACKGROUND

Surgical stapling apparatus for stapling tissue are well known in theart and typically include a handle assembly, a body portion extendingdistally from the handle assembly, and a tool assembly supported on adistal end of the body portion. The tool assembly includes first andsecond jaws which are movable in relation to each other between open orunapproximated and approximated positions. The first jaw supports ananvil assembly and the second jaw supports a cartridge which houses aplurality of staples. The cartridge can also include a knife forsevering tissue. In known apparatus, a fired or spent cartridge can bereplaced with an unfired or fresh cartridge to facilitate reuse of thesurgical stapling apparatus.

In order to prevent refiring of the surgical stapling apparatus with aspent cartridge, or to prevent firing of a surgical stapling apparatuswhich does not include a cartridge, it is known to provide a lockoutmechanism which prevents advancement of a drive member of the staplingapparatus. Although known lockout mechanisms are effective to preventfiring of a surgical stapling apparatus which includes a spent cartridgeor does not include a cartridge, an improved, reliable lockout mechanismis desired.

SUMMARY

A surgical stapling device includes a body portion defining alongitudinal axis having a proximal end and a distal end, a toolassembly supported on the distal end of the body portion, a driveassembly movably supported within the tool assembly from a retractedposition to an initial advanced position to move the tool assembly fromthe open position to the approximated position, and a firing lockoutassembly. The tool assembly includes an anvil assembly, a channel memberpivotally supported relative to the anvil assembly, and a cartridgeassembly releasable disposed within the channel member. The toolassembly is movable from an open position to an approximated position.The cartridge assembly supports a plurality of staples and includes anactuation sled movable between a retracted position and an advancedposition to eject the plurality of staples from the cartridge assembly.The drive assembly has a stop surface. The firing lockout assemblyincludes a latch member having a blocking portion. The latch member ispivotally supported within the tool assembly and is movable from a firstposition to a second position. In the first position, the blockingmember of the latch member is aligned with the stop surface of the drivemember to prevent advancement of the drive member within the toolassembly beyond the initial advanced position, and in the secondposition, the blocking member is misaligned with the stop surface of thedrive member to permit advancement of the drive member within the toolassembly beyond the initial advanced position. The actuation sled ispositioned to retain the latch member in its second position when theactuation sled is in its retracted position and the tool assembly is inthe approximated position.

In certain aspects of the disclosure, the actuation sled is positionedwithin the cartridge assembly to be engaged by the drive assemblysubsequent to the drive assembly moving to the initial advancedposition. Further advancement of the drive assembly may effect movementof the actuation sled from the retracted position to the advancedposition upon movement of the drive member from the initial advancedposition to a subsequent advanced position. The firing lockout assemblymay further include a biasing member positioned to urge the latch membertowards the first position.

In some aspects of the disclosure, the actuation sled includes anengagement feature, that engages the latch member to move the latchmember from the first position to the second position when tool assemblyis moved to the approximated position and the actuation sled is in theretracted position. The latch member may include first and second legsextending distally from the blocking portion. Each of the first andsecond legs may support a pivot member.

The latch member may include an extension extending from one of thefirst and second legs. The extension may engage the engagement featureto move the latch member to the second position when the tool assemblyis moved to the closed position. Movement of the drive assembly beyondthe initial advanced position may move the actuation sled from theretracted position to the advanced position to eject the plurality ofstaples from the cartridge assembly.

In aspects of the disclosure, the drive assembly includes a body and aclamping member including an upper flange and a lower flangeinterconnected by a vertical strut. The clamping member may bepositioned to engage the actuation sled to move the actuation sleddistally within the cartridge assembly as the drive assembly moves fromits retracted position towards a fully advanced position. The body ofthe drive assembly includes the stop surface. The body of the driveassembly may include a guide surface for retaining the latch member inthe second position. The anvil assembly may define a first cam surfaceand the cartridge assembly may define a second cam surface. The upperand lower flanges of the clamping member of the drive assembly mayengage the first and second cam surfaces as the drive assembly movesfrom its retracted position to its initial advanced position to move thetool assembly to the approximated position.

In certain aspects of the disclosure, the blocking member of the latchmember is positioned to engage a bottom surface of the body of the driveassembly as the drive assembly is moved from its initial advancedposition towards its fully advanced position to retain the latch memberin the second position. The actuation sled may be in abuttingrelationship with the clamping member of the drive assembly such thatupon movement of the drive assembly from the advanced position back tothe retracted position, the actuation sled remains in its advancedposition.

Another surgical stapling device includes a body portion defining alongitudinal axis having a proximal end and a distal end, a toolassembly supported on the distal end of the body portion, a driveassembly movably supported within the tool assembly from a retractedposition to an initial advanced position to move the tool assembly fromthe open position to the approximated position, the drive assemblyhaving a stop surface, and a firing lockout assembly. The tool assemblyincludes an anvil assembly, a channel member pivotally supportedrelative to the anvil assembly, and a cartridge assembly releasabledisposed within the channel member. The tool assembly is movable from anopen position to an approximated position. The cartridge assemblysupports a plurality of staples and includes an actuation sled movablebetween a retracted position and an advanced position to eject theplurality of staples from the cartridge assembly. The firing lockoutassembly includes a latch member and a biasing member. The latch memberhas a blocking portion and is pivotally supported within the toolassembly between a first position to a second position. The biasingmember is configured to urge the latch member to the first position. Inthe first position, the blocking member of the latch member is alignedwith the stop surface of the drive member to prevent advancement of thedrive member within the tool assembly beyond the initial advancedposition. In the second position, the blocking member is misaligned withthe stop surface of the drive member to permit advancement of the drivemember within the tool assembly beyond the initial advanced position.The actuation sled is positioned to retain the latch member in itssecond position when the actuation sled is in its retracted position andthe tool assembly is in the approximated position.

In certain aspects of the disclosure, the actuation sled is positionedwithin the cartridge assembly to be engaged by the drive assemblysubsequent to the drive assembly moving to the initial advancedposition. Further advancement of the drive assembly may effect movementof the actuation sled from the retracted position to the advancedposition upon movement of the drive member from the initial advancedposition to a subsequent advanced position.

In some aspects of the disclosure, the actuation sled includes anengagement feature, that engages the latch member to move the latchmember from the first position to the second position when tool assemblyis moved to the approximated position and the actuation sled is in theretracted position. The latch member may include first and second legsextending distally from the blocking portion. Each of the first andsecond legs may support a pivot member. The latch member may include anextension extending from one of the first and second legs. The extensionmay engage the engagement feature to move the latch member to the secondposition when the tool assembly is moved to the closed position.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the disclosure are described herein with reference tothe drawings, wherein:

FIG. 1 is a side, perspective view of various aspects of the disclosedsurgical stapling apparatus including a loading unit having a toolassembly in an open position;

FIG. 2 is a side, perspective view of the loading unit shown in FIG. 1 ,with an anvil assembly of the tool assembly shown in phantom;

FIG. 3 is an enlarged, side perspective view of the indicated area ofdetail shown in FIG. 2 ;

FIG. 4 is a side perspective view with parts separated of the loadingunit shown in FIG. 2 ;

FIG. 5 is an enlarged, side perspective view of the indicated area ofdetail shown in FIG. 4 ;

FIG. 6 is a side, cross-sectional view taken along section line 6-6shown in FIG. 3 , with the tool assembly in the open position and alatch member of a lockout assembly in a first or locked position priorto firing of the surgical stapling apparatus;

FIG. 7 is an enlarged, side perspective view of the indicated area ofdetail shown in FIG. 6 ;

FIG. 8 is the side, cross-sectional view taken along section line 6-6shown in FIG. 3 , with the tool assembly in a closed position and thelatch member in a first unlocked position prior to firing of thesurgical stapling apparatus;

FIG. 9 is an enlarged, side perspective view of the indicated area ofdetail shown in FIG. 8 ;

FIG. 10 is the enlarged, side perspective view of FIG. 9 with theloading unit in a first partially fired condition and the latch memberin a second unlocked position;

FIG. 11 is the enlarged, side perspective view of FIG. 10 , with theloading unit in a second partially fired condition and the latch memberin a third unlocked position; and

FIG. 12 is the enlarged, side perspective view of FIG. 11 , with theloading unit in a post-fired condition and the latch member in thelocked position.

DETAILED DESCRIPTION

The disclosed surgical stapling device will now be described in detailwith reference to the drawings in which like reference numeralsdesignate identical or corresponding elements in each of the severalviews. However, it is to be understood that the disclosed aspects of thedisclosure are merely exemplary of the disclosure and may be embodied invarious forms. Well-known functions or constructions are not describedin detail to avoid obscuring the disclosure in unnecessary detail.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as a basis for theclaims and as a representative basis for teaching one skilled in the artto variously employ the disclosure in virtually any appropriatelydetailed structure. In addition, directional terms such as front, rear,upper, lower, top, bottom, distal, proximal, and similar terms are usedto assist in understanding the description and are not intended to limitthe disclosure.

In this description, the term “proximal” is used generally to refer tothat portion of the device that is closer to a clinician, while the term“distal” is used generally to refer to that portion of the device thatis farther from the clinician. In addition, the term “clinician” is usedgenerally to refer to medical personnel including doctors, nurses, andsupport personnel.

The disclosed surgical stapling device includes a firing lockoutassembly configured to prevent firing of the surgical stapling devicewhen the surgical stapling device is not loaded or loaded with a spentcartridge assembly.

FIG. 1 illustrates a surgical stapling device according to exemplaryaspects of the disclosure, shown generally as stapling device 10. Thestapling device 10 includes a powered handle assembly 20, an adapterassembly 30 releasably secured to the powered handle assembly 20, and aloading unit 100 releasably secured to the adapter assembly 30. Althoughshown as individual or separable components, it is envisioned that anyor all of the powered handle assembly 20, adapter assembly 30, andloading unit 100 may be integrally formed.

FIGS. 2-4 illustrate the loading unit 100 of the surgical staplingdevice 10 (FIG. 1 ) including a body portion 102 and a tool assembly 104pivotally secured to the body portion 102. The tool assembly 104includes a jaw assembly 106 including an anvil assembly 114, a channelmember 118, and a cartridge assembly 116 that is received within thechannel member 118. The anvil assembly 114 and cartridge assembly 116are pivotable relative to each other between an open position (FIG. 2 )and an approximated or clamped position (FIG. 8 ). A mounting assembly120 pivotally couples the proximal body portion 102 of the loading unit100 and the tool assembly 104. A drive assembly 130 (FIG. 4 ) whichincludes a dynamic clamping member 132 (FIG. 3 ) extends from the bodyportion 102 of the loading unit 100, through the mounting assembly 120into the tool assembly 104. As will be described below, a firing lockoutassembly 140 is supported within the tool assembly 104 to prevent thedrive assembly 130 from being advanced beyond an initial advancedposition in the absence of an unfired cartridge assembly 116 receivedwithin the channel member 118 of the jaw assembly 106.

The loading unit 100 is substantially as described in U.S. Pat. No.9,016,539 (“the '539 patent”). Accordingly, the components of theloading unit 100 which are common to that which is disclosed in the '539patent will only be described herein to the extent necessary to fullydisclose the aspects of the firing lockout assembly 140 and its methodof operation.

The anvil assembly 114 of the jaw assembly 106 includes an anvil body150 and an anvil plate 152. The anvil plate 152 is secured to theunderside of the anvil body 150 to define a channel 151 (FIG. 7 ) forreceiving a portion of the dynamic clamping member 132 of the driveassembly 130 of the loading unit 100. The anvil plate 152 definesplurality of staple receiving depressions (not shown).

The cartridge assembly 116 of the jaw assembly 106 includes a cartridgebody 156, a plurality of staples “5”, and a staple firing assembly 160that includes an actuation sled 162 and a plurality of pusher members164. The cartridge assembly 116 is releasably supported in the channelmember 118. The cartridge body 156 is secured to the channel member 118with a snap-fit connection. Other forms of connection are contemplatedand may be used in place of the snap-fit connection, or in additionthereto. The channel member 118 is pivotally secured to the anvil body150. The cartridge body 156 defines a plurality of laterally spacedstaple retention slots 153 which are positioned in alignment with thestaple receiving depressions (not shown) in the anvil plate 152 of theanvil assembly 114. Each slot 153 is configured to receive a fastener orstaple “S” and a pusher 164. The actuation sled 162 is positioned withinthe cartridge body 156 of the cartridge assembly 116 and is configuredto pass longitudinally through the cartridge body 156 into engagementwith the pushers 164 to sequentially eject the staples “S” from thecartridge body 156.

The mounting assembly 120 includes an upper mounting member 170 (FIG. 4) and a lower mounting member 172 secured to the tool assembly 104.First and second coupling members 176, 178 pivotally secure the upperand lower mounting members 170, 172 to the proximal body portion 102 ofthe loading unit 100. The body portion 102 of the loading unit 100includes upper and lower housing halves 180, 182 which are containedwithin an outer sleeve 184 (FIG. 2 ). The upper and lower housing halves180, 182 (FIG. 4 ) define a channel 181 for slidably receiving the driveassembly 130.

The drive assembly 130 includes the dynamic clamping member 132 and abody 134. In certain aspects of the disclosure, the body 134 of thedrive assembly 130 is formed from a plurality of stacked sheets that areformed of a resilient or flexible material, e.g., stainless steel. Thedynamic clamping member 132 includes an upper flange 136 a, a lowerflange 136 b, and a vertical strut 138 interconnecting the upper flange136 a and the lower flange 136 b. A knife 138 a is supported on orformed into the vertical strut 138 of the dynamic clamping member 132.The upper flange 136 a is positioned to be slidably received within thechannel 151 (FIG. 7 ) of the anvil assembly 114 and the lower flange 136b is positioned to be slidably positioned along an outer surface 118 a(FIG. 6 ) of the channel member 118.

The distal portion of the body 134 of the drive assembly 130 supportsthe dynamic clamping member 132 of the drive assembly 130 and includes astop surface 133 that is configured for engagement with the firinglockout assembly 140 when no cartridge assembly or a spent cartridgeassembly 116 is loaded into the channel assembly 118 of the loading unit100. The drive assembly 130 may further include a guide surface 135 toretain the firing lockout assembly 140 in its unlocked position as thedynamic clamping member 132 is advanced through the cartridge assembly116.

When the stapling device 10 is operated, distal movement of the driveassembly 130 to the initial advanced position (FIG. 8 ) advances theupper flange 136 a of the dynamic clamping member 132 of the driveassembly 130 into a cam surface 153 (FIG. 7 ) formed on the anvil plate152 and advances the lower flange 136 b of the dynamic clamping member132 of the drive assembly 130 into engagement with a cam surface 131formed on the channel member 118 of the jaw assembly 106 to pivot thecartridge assembly 116 from the open position towards the anvil assembly114 to the approximated position (FIG. 8 ). Continued advancement of thedrive assembly 130 beyond the initial advanced position progressivelymaintains a minimum tissue gap adjacent the dynamic clamping member 132of the drive assembly 130 as the dynamic clamping member 132 movesthrough the jaw assembly 106.

FIG. 5 illustrates the proximal end of the channel member 118 of the jawassembly 106, the firing lockout assembly 140, and the actuation sled162 of the stapling assembly 160. The actuation sled 162 of thecartridge assembly 116 is disposed within the cartridge body 156 at aposition distal of the dynamic clamping member 132 of the drive assembly130. The actuation sled 162 includes a plurality of cam surfaces 165(FIG. 5 ) that engage the pushers 164 (FIG. 4 ) within the cartridgebody 156 to eject the staples “S” from the cartridge body 156 when theactuation sled 162 is advanced through the jaw assembly 106. A proximalend of the actuation sled 162 includes an engagement feature 162 a (FIG.5 ).

The firing lockout assembly 140 of the loading unit 100 includes a latchmember 200 and a biasing member 230, e.g., a leaf spring. The latchmember 200 is pivotally supported on a proximal portion of the channelmember 118 of the jaw assembly 106. The latch member 200 includes aU-shaped body having a base or blocking portion 202 and first and secondlegs 204, 206 extending distally from the base 202. The blocking portion202 includes a proximal surface 202 a. In the absence of the actuationsled 162 of the stapling assembly 160, the proximal surface 202 a of theblocking portion 202 engages the stop surface 133 of the drive assembly130 to prevent advancement of the drive assembly 130 beyond its initialadvanced position (FIG. 8 ) The latch member 200 includes a pivot member208 that extends outwardly from each of the first and second legs 204,206 for pivotally securing the latch member 200 relative to the channelmember 118. The latch member 200 is pivotal from a first or lockedposition (FIG. 7 ) wherein the blocking portion 202 is aligned with thestop surface 133 of the drive assembly 130 to prevent advancement of thedrive assembly 130 within the tool assembly 104 and a second or unlockedposition (FIG. 9 ) wherein the blocking portion 202 is misaligned withthe stop surface 133 of the drive assembly 130 to permit advancement ofthe drive assembly 130 within the tool assembly 104 beyond its initialadvanced position.

The latch member 200 includes an extension 210 extending distally from adistal portion of the first leg 204. The extension 210 engages anengagement feature 162 a of the actuation sled 162 when a pre-firedcartridge assembly 116 is loaded within the channel member 118 of thejaw assembly 106 of the loading unit 100. When the extension 210 is inengagement with the engagement feature 162 a of the actuation sled 162,pivoting of the jaw assembly 106 to the approximated position throughadvancement of the drive assembly 130 to its initial advanced positioncauses the latch member 200 to pivot to its second or unlocked position,thereby moving the blocking portion 202 of the latch member 200 out ofalignment with the stop surface 133 of the drive assembly 130. When theblocking portion 202 of the latch member 200 is misaligned with the stopsurface 133, i.e., the latch member 200 is in the unlocked position, thedrive assembly 130 may be advanced through the cartridge assembly 116.The biasing member 230, urges the latch member 200 towards the first orlocked position to engage the latch member 200 with the stop surface 133of the drive assembly 130 in the absence of the actuation sled 162. Theactuation sled 162 is absent when a cartridge assembly 116 is notreceived within the channel member 118 of the jaw assembly 106, or whena spent or previously fired cartridge assembly 116 is loaded within thechannel member 118.

FIGS. 6 and 7 illustrate the jaw assembly 106 of the loading unit 100 inthe open position with a pre-fired or unused cartridge assembly 116received within the channel member 118. When the jaw assembly 106 is inthe open position, regardless of the presence of a cartridge assembly116 in the channel member 118, the biasing member 230 urges the firinglockout assembly 140 to the locked position. In this manner, theblocking portion 202 of the latch member 200 is in alignment with thestop surface 133 of the body 134 of the drive assembly 130, therebypreventing significant advancement of the drive assembly 130, i.e.,beyond the initial advanced position. As shown in FIG. 7 , the stopsurface 133 of the drive assembly 130 is longitudinally spaced from theblocking portion 202 of the latch member 200 to permit the initialmovement of the drive assembly 130 from a fully retracted position tothe initial advanced position to allow the drive assembly 130 to cam thejaw assembly 106 to the approximated position. Similarly, the actuationsled 162 of the stapling assembly 160 is longitudinally spaced from thedynamic clamping member 132 of the drive assembly 130 to accommodate theinitial advancement of the drive assembly 130 to allow for movement ofthe jaw assembly 106 to the approximated position.

When a pre-fired cartridge assembly 116 is received within the channelmember 118 of the jaw assembly 106, the actuation sled 162 of thecartridge assembly 116 is in a proximal-most or fully retractedposition. As noted above, in a pre-fired position with the dynamicclamping member 132 in its fully retracted position, the actuation sled162 is longitudinally spaced from the dynamic clamping member 132 of thedrive assembly 130. This arrangement permits initial advancement of thedrive assembly 130 to cause the closing of the jaw assembly 106 withoutadvancing the actuation sled 162. The extension 210 of the latch member200 at least aligns with, if not engages, the engagement feature 162 aof the actuation sled 162.

FIGS. 8 and 9 illustrate the jaw assembly 106 of the tool assembly 104of the loading unit 100 in the approximated position. As noted above,the jaw assembly 106 is moved to the approximated position, as indicatedby arrow “A” in FIG. 8 , through initial advancement of the dynamicclamping member 132 of the drive assembly 130 in the direction indicatedby arrow “B” in FIG. 9 . More particularly, advancement of the dynamicclamping member 132 of the drive assembly 130 in the direction of arrow“B” causes the upper flange 136 a of the dynamic clamping member 132 toengage the cam surface 153 of the anvil plate 152 and the lower flange136 b of the dynamic clamping member 132 to engage the cam surface 131of the channel member 118 to pivot the cartridge assembly 116 towardsthe anvil assembly 114 in the direction indicated by arrow “A”.

As the cartridge assembly 116 pivots relative to the anvil assembly 114during initial advancement of the drive assembly 130, the latch member200 of the firing lockout assembly 140 pivots against the urging ofbiasing member 230 (FIG. 5 ), as indicated by arrow “C” in FIG. 9 , tothe unlocked position. The latch member 200 is moved to the unlockedposition through engagement of the extension 210 of the latch member 200with the engagement feature 162 a of the actuation sled 162 of thecartridge assembly 116. Pivoting of the cartridge assembly 116 relativeto the anvil assembly 114 causes corresponding pivoting of the latchmember 200 relative to the drive assembly 130.

In the unlocked position, the blocking portion 202 of the latch member200 is disposed out of alignment with the stop surface 133 of the driveassembly 130. As shown, the blocking portion 202 of the latch member 200is disposed in alignment with the guide surface 135 of the driveassembly 130 to facilitate distal movement of the drive assembly 130past the latch member 200.

FIG. 10 illustrates the loading unit 100 as the dynamic clamping member132 is advanced to move the actuation sled 162 distally through the toolassembly 104. When the dynamic clamping 132 is advanced through the toolassembly 104 in the direction indicated by arrow “D”, the blockingportion 202 of the latch member 200 of the firing lockout assembly 140engages the guide surface 135 of the drive assembly 130 to retain thelatch member 200 in the unlocked position.

FIG. 11 illustrates the loading unit 100 as the drive assembly 130 isadvanced in the direction indicated by arrow “E” to advance theactuation sled 162. As actuation sled 162 advances, staples “S” (FIG. 4) are ejected from the staple cartridge 156 of the cartridge assembly116. Subsequent to advancement of the stop surface 133 of the driveassembly 130 past the blocking portion 202 of the latch member 200 ofthe firing lockout assembly 140, the latch member 200 is maintained inthe unlocked position through engagement of the blocking portion 202 ofthe latch member 200 with an undersurface 134 a of the body 134 of thedrive assembly 130.

FIG. 12 illustrates the loading unit 100 subsequent to firing of thecartridge assembly 116, and prior to the drive assembly 130 returning toa fully-retracted position. During retraction of the drive assembly 130,the latch member 200 of the firing lockout assembly 140 remains in theunlocked position through engagement of the blocking portion 202 of thelatch member 200 with the undersurface 134 a of the body 134 of thedrive assembly 130. Once the stop surface 133 of the drive assembly 130is retracted beyond the blocking portion 202 of the latch member 200 andthe dynamic clamping member 132 has moved proximally of the latch member200, in the absence of the actuation sled 162 a of the cartridgeassembly 116, the biasing member 230 of the firing lockout assembly 140biases the latch member 200 to the locked position. In the lockedposition, the drive assembly 130 is prevented from advancing beyond theinitial advanced position through engagement of the blocking portion 202of the latch member 200 with the stop surface 133 of the drive assembly130, thereby preventing further advancement of the drive assembly 130.

To reuse stapling device 10, the drive assembly 130 is fully retractedto cause the opening of the jaw assembly 106. When the dynamic clampingmember 132 is in the fully retracted position, a biasing member (notshown) urges the jaw assembly 106 to the open position. The spentcartridge assembly is then removed from the channel member 118 and a newcartridge assembly 116 is positioned within the channel member 118. Asthe new cartridge assembly 116 includes an actuation sled 162 positionedsuch that an engagement feature 162 of the actuation sled 162 alignswith the extension 210 of the latch member 200 to cause the latch member200 to move to the unlocked position when the drive assembly 130 isinitially advanced to cause the closing of the jaw assembly 106, and thefurther firing of the stapling device 10.

Persons skilled in the art will understand that the devices and methodsspecifically described herein and illustrated in the accompanyingdrawings are non-limiting exemplary aspects. It is envisioned that theelements and features illustrated or described in connection with theexemplary aspects may be combined with the elements and features ofanother without departing from the scope of the disclosure. As well, oneskilled in the art will appreciate further features and advantages ofthe disclosure based on the above-described aspects. Accordingly, thedisclosure is not to be limited by what has been particularly shown anddescribed, except as indicated by the appended claims.

What is claimed is:
 1. A loading unit for a surgical stapling device,the loading unit comprising: a body portion defining a longitudinal axishaving a proximal portion and a distal portion; a tool assemblysupported on the distal portion of the body portion, the tool assemblyincluding an anvil assembly and a channel member pivotally supportedrelative to the anvil assembly, the channel member being configured toreleasably receive a cartridge assembly, the tool assembly being movablefrom an open condition to an approximated condition; a drive assemblysupported within the tool assembly and movable from a retracted positionto an initial advanced position to move the tool assembly from the opencondition to the approximated condition, and movable from the initialadvanced position to a fully advanced position to effect movement of anactuation sled from a sled retracted position to a sled advancedposition, the drive assembly having a stop surface and an angled guidesurface that is contiguous with the stop surface; and a firing lockoutassembly including a latch member having a blocking portion, the latchmember being pivotally supported within the tool assembly and movablebetween a first position and a second position, wherein in the firstposition the blocking portion of the latch member is aligned with thestop surface of the drive assembly to prevent advancement of the driveassembly within the tool assembly beyond the initial advanced positionand in the second position the blocking portion is misaligned with thestop surface of the drive assembly to permit advancement of the driveassembly within the tool assembly beyond the initial advanced position,wherein the latch member remains in the first position as the toolassembly moves to the approximated condition in an absence of acartridge assembly having an actuation sled in a sled retracted positionreceived within the channel member, wherein the angled guide surface ofthe drive assembly is configured to engage the blocking portion of thelatch member as the drive assembly moves from the initial advancedposition to the fully advanced position to urge the latch member to thesecond position.
 2. The loading unit of claim 1, further including acartridge assembly received within the channel member, the cartridgeassembly including the actuation sled, the actuation sled positionedwithin the cartridge assembly to be engaged by the drive assembly andmovable from the sled retracted position to the sled advanced position.3. The loading unit of claim 2, wherein the firing lockout assemblyfurther includes a biasing member, the biasing member being positionedto urge the latch member towards the first position.
 4. The loading unitof claim 3, wherein the actuation sled includes an engagement feature,the engagement feature engaging the latch member to move the latchmember from the first position to the second position when the toolassembly is moved to the approximated condition and the actuation sledis in the sled retracted position.
 5. The loading unit of claim 4,wherein the latch member includes first and second legs extendingdistally from the blocking portion, each of the first and second legssupporting a pivot member.
 6. The loading unit of claim 5, wherein thelatch member includes an extension extending from one of the first orsecond legs, the extension engaging the engagement feature to move thelatch member to the second position when the tool assembly is moved tothe approximated condition.
 7. The loading unit of claim 2, whereinmovement of the drive assembly beyond the initial advanced positionmoves the actuation sled from the sled retracted position towards thesled advanced position to eject a plurality of staples from thecartridge assembly.
 8. The loading unit of claim 1, wherein the driveassembly includes a body and a clamping member having an upper flangeand a lower flange interconnected by a vertical strut, the clampingmember being positioned to engage the actuation sled to move theactuation sled distally within the cartridge assembly as the driveassembly moves from the initial advanced position towards the fullyadvanced position.
 9. The loading unit of claim 8, wherein the body ofthe drive assembly includes the stop surface and the angled guidesurface.
 10. The loading unit of claim 8, wherein the anvil assemblydefines a first cam surface and the cartridge assembly defines a secondcam surface, the upper and lower flanges of the clamping member of thedrive assembly engaging the first and second cam surfaces as the driveassembly moves from the retracted position to the initial advancedposition to move the tool assembly to the approximated condition. 11.The loading unit of claim 10, wherein the blocking portion of the latchmember is positioned to engage a bottom surface of the body of the driveassembly as the drive assembly is moved from the initial advancedposition towards the fully advanced position to retain the latch memberin the second position.
 12. The loading unit of claim 10, wherein theactuation sled is in abutting relationship with the clamping member ofthe drive assembly such that upon movement of the drive assembly fromthe fully advanced position back towards the retracted position, theactuation sled remains in the sled advanced position.
 13. A surgicalstapling device comprising: a body portion defining a longitudinal axishaving a proximal portion and a distal portion; a tool assemblysupported on the distal portion of the body portion, the tool assemblyincluding an anvil assembly and a channel member pivotally supportedrelative to the anvil assembly, the channel member being configured toreleasably receive a cartridge assembly, the tool assembly being movablefrom an open condition to an approximated condition; a drive assemblysupported within the tool assembly and movable from a retracted positionto an initial advanced position to move the tool assembly from the opencondition to the approximated condition, and movable from the initialadvanced position to a fully advanced position to effect movement of anactuation sled from a sled retracted position to a sled advancedposition, the drive assembly having a stop surface and an angled guidesurface that is contiguous with the stop surface; and a firing lockoutassembly including a latch member and a biasing member, the latch memberhaving a blocking portion and being pivotally supported within the toolassembly between a first position and a second position, the biasingmember being configured to urge the latch member to the first position,wherein in the first position, the blocking portion of the latch memberis aligned with the stop surface of the drive assembly to preventadvancement of the drive assembly within the tool assembly beyond theinitial advanced position and in the second position the blockingportion is misaligned with the stop surface of the drive assembly topermit advancement of the drive assembly within the tool assembly beyondthe initial advanced position, wherein the latch member remains in thefirst position as the tool assembly moves to the approximated conditionin an absence of a cartridge assembly having the actuation sled in thesled retracted position being received within the channel member,wherein the angled guide surface of the drive assembly is configured toengage the blocking portion of the latch member as the drive assemblymoves from the initial advanced position to the fully advanced positionto urge the latch member to the second position.
 14. The surgicalstapling device of claim 13, further including a cartridge assemblyreceived within the channel member, the cartridge assembly including theactuation sled, wherein the actuation sled is positioned within thecartridge assembly to be engaged by the drive assembly subsequent to thedrive assembly moving to the initial advanced position.
 15. The surgicalstapling device of claim 14, wherein the actuation sled includes anengagement feature, the engagement feature engaging the latch member tomove the latch member from the first position to the second positionwhen tool assembly is moved to the approximated condition and theactuation sled is in the sled retracted position.
 16. The surgicalstapling device of claim 15, wherein the latch member includes first andsecond legs extending distally from the blocking portion, each of thefirst and second legs supporting a pivot member.